The present invention relates to a continuously operating press for the production of boards, such as chip boards, fiber boards and the like comprising two endless plate belts arranged one above the other and consisting of plates pivoted (articulated) to one another and rotating about parallel horizontal axes. The runs of the endless plate belts facing each other are driveable in the same direction by press-on drums or rollers and each endless plate belt is surrounded by an endless steel band. Presses of this kind have proven superior compared with presses in which the endless plate belts are driven by polygonal drums with plates being provided in place of press-on drums, while thereby the starting energy of the endless plates are considerably reduced. Such presses are primarily used as preliminary presses in which at least the endless plate belts may be heated preferably by gas burners. Also, the endless steel bands surrounding the endless plate bands may be heated.
If, for example, a chip cake or fleece is first passed through a preliminary press in order to be subsequently compressed into a chip board in a finishing press, then a pressure of 15 to 20 kg/cm.sup.2 under normal conditions, is exerted on the chip cake as it passes through the preliminary press in order to complete the chip cake such that it will not be damaged during further transport to the finishing press. In such a situation, it is of no consequence whether the finishing press is constructed as a discontinuously or as a continuously operating press. When, however, relatively high pressures must be exerted on the chip cake, problems which cannot be understood arise. These problems are due to the fact that the particles or chips to be compressed into a board, after they have been deposited and spread over a base, preferably onto an endless transport band, do not hang together. Aside from the danger that a portion of the particles or chips or the like small at the upper side of the chip cake may be blown away during entry of the cake into the continuously operating press, (which problem has, in the meantime, now been overcome) the press, on account of exerting pressure, must be constructed very strong. Thus, the press must be relatively heavy and hence also relatively expensive, since the thicker the plates to be produced, the more expensive the press. In addition, when the width of the chip cake exceeds a certain value, the stress limit of the high-grade steel from which the endless plate belts are made, may be exceeded when the pressure is increased to the extent necessary to compress the chip cake and prevent individual chips of the chip cake from debonding from the cake when the cake, after leaving the preliminary press, is moved into a finishing press. It has been shown that the pressure exerted by the endless plate belts can only be increased to a certain value, for example, 20 kg/cm.sup.2.